Impedance Measurement - Dual Channel Method Using Transfer Function

This sequence demonstrates an alternative to the traditional SoundCheck single channel impedance measurement method. A white noise stimulus (10 Hz – 10 kHz) is played through the speaker while the signal across the amplifier terminals is recorded by Direct In 1 and the signal across the impedance box is recorded by Direct In 2. A transfer function analysis step is then applied to the recorded time waveforms to calculate the impedance curve. Subsequent post processing steps apply a frequency window, 1/24th octave smoothing and 1/24th octave resolution to the impedance curve. The curve is then post-processed to calculate resonance frequency, maximum impedance and Q of the resonance peak. A set of arbitrary limits steps are also provided to generate pass/fail results. The final display shows the post processed impedance curves and results window. More